Recent studies have challenged the traditionally held view that lead poisoning, as regards the CNS, is a threshold illness, i.e., dangerous levels exist at 60-80 micrograms/100ml., and at levels below this, no disease as such exists. As one of the challengers, this laboratory has advanced the hypothesis that certain CNS dysfunctions, particularly mild and borderline mental retardation and hyperkinesis, may be conditions for which lead levels below threshold (as presently defined) can be held in part responsible. Screening studies done here and elsewhere demonstrate that a significant number of children with CNS dysfunctions, particularly the two above, do in fact have increased but not threshold lead levels. Further, those children studied who had little or no discernable reason for their diagnosed dynsfunction were those in whom raised levels were present in the largest numbers and reached the highest levels. An attempt at gaining some insight into the nature of these highly suspicious associations will be made via a double blind treatment utilizing chelates and placebos for the retarded group and chelates, placebos and methylphenidate for the hyperkinetic group. Children accepted for the treatment will be between 4-12 who have these conditions and who also have increased (22-55 micrograms/100ml.) lead levels. Measurements of intelligence, social competence, behavior, school achievement, learning, perceptual motor skills, and motoric activity will be taken before and after treatment. Outcome comparisons will be done within and between regimens using covariance analysis.